Open Loop Cooling Water System Having Recirculation Pump

ABSTRACT

An open loop cooling water system is for a marine engine. A cooling water inlet receives cooling water from a body of water. A cooling water outlet discharges the cooling water back to the body of water. A cooling water circuit conveys cooling water from the cooling water inlet, through the marine engine, and to the cooling water outlet. A cooling water pump that pumps cooling water from upstream to downstream through the cooling water circuit. A recirculation pump that is located in the cooling water circuit downstream of at least one component of the marine engine and upstream of the cooling water outlet. The recirculation pump is configured to pump cooling water from downstream of the marine engine back into the cooling water circuit upstream of the marine engine. Methods are for cooling a marine engine using an open loop cooling system.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 61/945,317, filed Feb. 27, 2014.

FIELD

The present disclosure relates to cooling systems for internal combustion engines, particularly internal combustion engines associated with marine propulsion devices, including outboard marine propulsion devices for marine vessels.

BACKGROUND

U.S. Pat. No. 8,500,501 discloses an outboard marine drive that includes a cooling system drawing cooling water from a body of water in which the outboard marine drive is operating, and supplying the cooling water through cooling passages in an exhaust tube in the driveshaft housing, a catalyst housing, and an exhaust manifold, and thereafter through cooling passages in the cylinder head and the cylinder block of the engine. A 3-pass exhaust manifold is provided. A method is provided for preventing condensate formation in a cylinder head, catalyst housing, and exhaust manifold of an internal combustion engine of a powerhead in an outboard marine drive.

U.S. Pat. No. 7,421,983 discloses a cooling system for a marine propulsion device that provides a closed portion of the cooling system which recirculates coolant through the engine block and cylinder head, the exhaust manifold, and the exhaust elbow. It provides a pressure relief cap connected to the exhaust elbow and a low velocity portion of the coolant jacket of the exhaust elbow to facilitate the release of gas and coolant when pressures exceed a preselected magnitude.

U.S. Pat. No. 7,398,745 discloses a cooling system for a marine propulsion device that provides a bypass loop around a cooling pump that allows the flow of cooling water through certain components to be reduced or increased as a function of the temperature of those components while causing a full flow of cooling water to flow through other selected heat emitting devices. Using this configuration of components and bypass conduits, the operating condition of the cooling water pump can be continually monitored, including the condition of its flexible vanes. By observing the effective cooling capacity of the system under conditions with the bypass valve open and closed, the effectiveness of the cooling water pump can be assessed and a suggestion of maintenance can be provided.

U.S. Pat. No. 7,370,611 discloses a cooling system for a marine propulsion device which provides a bypass loop around a cooling pump that allows the flow of cooling water through certain components to be reduced or increased as a function of the temperature of those components while causing a full flow of cooling water to flow through other selected heat emitting devices. Using this configuration of components and bypass conduits, the operating condition of the cooling water pump can be continually monitored, including the condition of its flexible vanes. By observing the effective cooling capacity of the system under conditions with the bypass valve open and closed, the effectiveness of the cooling water pump can be assessed and a suggestion of maintenance can be provided.

U.S. Pat. No. 7,264,520 discloses a cooling system for an outboard motor that pumps water from a body of water through certain selected portions of the outboard motor and through a heat exchanger. A coolant conduit is directed to conduct the coolant in thermal communication with various portions of the outboard motor. The engine block is cooled by a flow of the coolant and an engine head is cooled by a flow of water from the body of water. Other heat emitting devices are connected in thermal and fluid communication with the water and coolant conduits.

U.S. Pat. No. 7,114,469 discloses a cooling system for a marine engine that divides a flow of cooling water into first and second streams downstream of a pump. The first stream flows through a first cooling system which is controlled by a pressure sensitive valve. The second stream flows through a second cooling system which is controlled by a temperature sensitive valve.

SUMMARY

This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

In certain examples, an open loop cooling water system is for a marine engine. A cooling water inlet receives cooling water from a body of water. A cooling water outlet discharges the cooling water back to the body of water. A cooling water circuit conveys cooling water from the cooling water inlet, through the marine engine, and to the cooling water outlet. A cooling water pump pumps cooling water from upstream to downstream through the cooling water circuit. A recirculation pump is located in the cooling water circuit downstream of at least one component of the marine engine and upstream of the cooling water outlet. The recirculation pump is configured to pump cooling water from downstream of the at least one component of the marine engine back into the cooling water circuit upstream of the marine engine.

In certain examples, methods are for cooling a marine engine. The methods can comprise (1) pumping cooling water from upstream to downstream through a cooling water circuit that conveys cooling water from the cooling water inlet, through the marine engine, and to the cooling water outlet; and (2) pumping cooling water that is located in the cooling water circuit downstream of at least one component of the marine engine and upstream of the cooling water outlet back into the cooling water circuit upstream of the marine engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is described with reference to the following Figures. The same numbers are used throughout the Figures to reference like features and like components.

FIG. 1 depicts one example of an open loop cooling water system for a marine engine.

FIG. 2 depicts another example of an open loop cooling water system for a marine engine.

FIG. 3 depicts a portion of a marine engine having a cam shaft and a mechanical recirculation pump that is mounted on the cam shaft and pumps cooling water from downstream of the marine engine back into a cooling water circuit upstream of the marine engine.

FIGS. 4-6 depict one example of the mechanical recirculation pump shown in FIG. 3.

FIG. 7 is a graph depicting temperature data taken from a prior art outboard marine engine.

FIG. 8 is a graph depicting temperature data taken from an outboard marine engine according the present disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

Through research and experimentation, the present inventors have determined that open loop cooling water systems for marine engines have certain disadvantages when compared to closed loop cooling water systems. In open loop cooling water systems, the temperature of the body of water in which the marine vessel operates dictates the temperature of the cooling water entering the marine engine. This becomes problematic in colder conditions when one of the first components cooled in the system is likely to be overcooled, which can result in one or more of the issues shown in the following table:

Potential Issues Caused by Overly Cold Water in Cooling System First Component cooled Primary Issue Exhaust Manifold Exhaust Condensation Oil Oil Condensation (milky) Cylinder Head -Exhaust Exhaust Condensation Cylinder Head - Intake Fuel Dilution/Emissions Cylinder Block Fuel Dilution

Certain open loop cooling water systems for conventional four stroke outboard marine engines first cool the exhaust tube and exhaust manifold. This typically creates condensation in the exhaust tube and exhaust manifold. In non-catalyst exhaust manifolds, such condensation typically does not present a problem because the exhaust manifold is oriented to safely drain the condensate from the exhaust manifold. However, the present inventors have found that if a catalyst is added to the system, condensate that forms in the exhaust gases may damage oxygen sensors associated with the catalyst or the catalyst itself.

The present inventors have thus endeavored to rectify these problems associated with open loop cooling water systems. In certain examples described herein below, a secondary water pump (i.e. a circulation pump that is in addition to the primary water pump typically located in the gear case of the outboard marine engine) is added to the system and configured to obtain relatively warm cooling water from near to the end of the cooling system and introduce the relatively warm cooling water back into the system early in the cooling system circuit, i.e. upstream of the marine engine. In some examples, this can be accomplished by introducing the water back into the system after or in a parallel branch to the location of a tell-tale, an exhaust sprayer, and/or other orifice-controlled flow paths from the system.

FIG. 7 depicts temperature data taken from an outboard marine engine that operates without the above described secondary water pump (circulation pump). As shown, the metal temperature is nearly the same as the incoming water temperature. The target for eliminating condensation from the exhaust system is 52 degrees, but the value for the metal temperature undesirably is only 28 degrees, even though the engine is operating in nominal water conditions (23 degrees).

In contrast, FIG. 8 depicts temperature data taken from an outboard marine engine according to the present disclosure, wherein the outboard marine engine includes a recirculation pump that is located in the cooling water circuit downstream of the marine engine and upstream of the cooling water outlet, and wherein the recirculation pump is configured to pump cooling water from downstream of the engine back into the cooling water circuit upstream of the engine. As shown, the metal and water temperatures advantageously are both above a minimum target value, even in cold water conditions (4 degrees).

FIG. 1 depicts one example of an open loop cooling water system 10 according to the present disclosure. A cooling water inlet 12 is located on a gear case 14 of the marine engine and receives cooling water from the body of water in which the marine propulsion device is operating. A cooling water outlet 16 is located in a midsection 18 of the outboard marine engine and discharges the cooling water back to the body of water. A cooling water circuit 20 conveys the cooling water from the cooling water inlet 12, through various components of the marine engine, and to the cooling water outlet 16. A cooling water pump 22 (primary pump) is located in the gear case 14 and connected to the cooling water inlet 12. The cooling water pump 22 pumps the cooling water from upstream to downstream through the cooling water circuit 20.

The outboard marine engine includes a cylinder head 24, a cylinder block 26 for containing combustion, an exhaust manifold 28 that receives exhaust gases from the combustion event and conveys the exhaust gases to an exhaust tube 30, and the exhaust tube 30 which conveys the exhaust gases from the exhaust manifold 28 to the midsection 18 of the outboard marine engine. Ultimately, the exhaust gases are discharged through the gear case 14 and typically through a propeller shaft housing associated with the outboard marine engine. A catalyst housing 32 is disposed in the exhaust manifold 28 or between the exhaust manifold 28 and the exhaust tube 30. The catalyst housing 32 contains a catalyst 34 for treating exhaust gases that are discharged from the outboard marine engine.

The cooling water circuit conveys cooling water from upstream to downstream through the noted components of the marine engine to thereby cool the components of the marine engine. The particular configuration of the cooling water circuit 20 can vary. In this example, the cooling water circuit includes, in series, an exhaust tube water jacket 36 on the exhaust tube 30, a catalyst housing water jacket 38 on the catalyst housing 32, an exhaust manifold water jacket 40 on the exhaust manifold 28, and at least one cooling water passage 42 through the noted cylinder block 26 and cylinder head 24 of the marine engine. The cooling water pump 22 pumps cooling water in series from the body of water, through the exhaust tube water jacket 36, catalyst housing water jacket 38, exhaust manifold water jacket 40 and cooling water passage 42. As is conventional, each of the water jackets and passages are configured such that heat is exchanged between the associated engine component and the cooling water flowing through the water jacket and passage. Thus, the cooling water cools the various components of the marine engine. The exhaust tube water jacket 36 conveys the cooling water to the catalyst housing water jacket 38, which carries cooling water to the exhaust manifold water jacket 40, which conveys cooling water to the cooling water passages 42 in the cylinder block 26 and cylinder head 24.

A recirculation pump 44 is located in the cooling water circuit 20 downstream of the components of the marine engine and upstream of the cooling water outlet 16. The recirculation pump 44 is configured to pump relatively warm cooling water from downstream of the at least one cooling passage in the marine engine back into the cooling water circuit 20 to mix with relatively cold cooling water at a location upstream of the marine engine. In this example, a recirculation passage 46 extends from the recirculation pump 44 to the cooling water circuit 20 at a recirculation location 48, which is upstream of the marine engine in the cooling water circuit 20. Advantageously, the recirculation location 48 is located downstream of all non-controlled (e.g. orifice-controlled) exit flow paths from the cooling water circuit 20, including a tell-tale outlet 50 and an exhaust sprayer 52 configured to spray cooling water into a flow of exhaust from the marine engine.

In this example, the recirculation pump 44 is an electric pump that is electrically powered. One example of a suitable electric pump is sold by Bosch, auxiliary water pump PAD2, PCE. Advantageously, this embodiment can be fairly small in size while still providing the benefits described herein. The small size greatly simplifies packaging of the recirculation pump 44 within the outboard marine engine.

FIG. 2 depicts another example of an open loop cooling water system 10. The example shown in FIG. 2 has many features that are the same or similar to the examples shown in FIG. 1 and like reference numbers are used to designate these features. In contrast to the example shown in FIG. 1, the open loop cooling water system 10 shown in FIG. 2 has a recirculation pump 44 that is a mechanical pump that is mechanically powered. The pump 44 is mounted on an exhaust cam shaft 54 of the marine engine such that rotation of the exhaust cam shaft 54 causes rotation of an impeller 56 located in a housing 58 of the recirculation pump 44.

FIGS. 3-6 depict one example of such a mechanical pump. As shown by arrows in FIGS. 5 and 6, cooling water axially flows into the housing 58 wherein rotation of the impeller 56 causes radially flow of cooling water out of the housing 58. The impeller 56 is off-center in the housing 58 such that the cooling water radially flows through the pump 44, as shown by the arrows in FIG. 5.

In other examples, the recirculation pump 44 can include a magnetic drive pump, such that a magnet on the impeller 56 or associated impeller shaft is magnetically coupled to a magnet on the top end of the cam shaft 54 with magnetic forces. The magnetic forces between the two magnets cause the pump impeller 56 to rotate as the cam shaft rotate. Such an arrangement could be configured such that there is no direct linkage between the pump impeller 56 and the cam shaft 54 so that no extra sealing features would be required to keep the oil and water separated (e.g. a solid wall could be disposed between the impeller 56 and the cam shaft 54).

The present disclosure thus provides a method of cooling a marine engine including pumping cooling water from upstream to downstream through a cooling water circuit 20 that conveys the cooling water from the cooing water inlet 12 through the marine engine and to the cooling water outlet 16. The method includes pumping cooling water that is located in the cooling water circuit 20 at a location downstream of at least one component of the marine engine and upstream of the cooling water outlet 16 back into the cooling water circuit 20 at a location upstream of the marine engine. The method can include pumping the cooling water that is located in the cooling water circuit 20 downstream of the component of the marine engine and upstream of the cooling water outlet 16 to a recirculation location 48 in the cooling water circuit 20 that is upstream of the marine engine. The recirculation location 48 is located in the cooling water jacket 36 on the exhaust tube 30, which carries exhaust gases from the marine engine.

The present disclosure thus provides a cooling water system 10 wherein the exhaust manifold 28 and exhaust tube 30 are cooled, in part, with recirculation cooling water, which prevents condensation in the exhaust manifold 28 and exhaust tube 30. In addition to the advantages and benefits noted above, the outboard marine engine cooling system having the recirculation pump 44 can also reduce thermostatic overshoot and thermostat cycling, which may lead to an increase in thermostat operating temperature. The configuration may also reduce leak rate, resulting in reduced engine warm up time.

In the above description, certain terms have been used for brevity, clarity, and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. The different systems and method steps described herein may be used alone or in combination with other systems and methods. It is to be expected that various equivalents, alternatives and modifications are possible within the scope of the appended claims. 

1. An open loop cooling water system for a marine engine, the open loop cooling water system comprising: a cooling water inlet that receives cooling water from a body of water; a cooling water outlet that discharges the cooling water back to the body of water; a cooling water circuit that conveys cooling water from the cooling water inlet, through the marine engine, and to the cooling water outlet; a cooling water pump that pumps cooling water from upstream to downstream through the cooling water circuit; and a recirculation pump that is located in the cooling water circuit downstream of at least one component of the marine engine and upstream of the cooling water outlet, wherein the recirculation pump is configured to pump cooling water from downstream of the at least one component of the marine engine back into the cooling water circuit upstream of the marine engine; a recirculation passage extending from the recirculation pump to the cooling water circuit at a recirculation location upstream of the marine engine, wherein the recirculation location is downstream of all non-controlled exit flow paths from the cooling water circuit.
 2. The open loop cooling water system according to claim 1, wherein the recirculation pump comprises an electric pump that is electrically powered.
 3. The open loop cooling water system according to claim 1, wherein the recirculation pump comprises a mechanical pump that is mechanically powered.
 4. (canceled)
 5. (canceled)
 6. The open loop cooling water system according to claim 1, wherein the non-controlled exit flow paths comprise at least one of a tell-tale outlet and an exhaust sprayer configured to spray cooling water into a flow of exhaust from the marine engine.
 7. The open loop cooling water system according to claim 1, wherein the cooling water circuit upstream of the marine engine comprises a water jacket on a catalyst housing, and wherein the recirculation location is upstream of the water jacket on the catalyst housing.
 8. The open loop cooling water system according to claim 1, wherein the cooling water circuit upstream of the marine engine comprises a water jacket on an exhaust tube of the marine engine, and wherein the recirculation passage extends from the recirculation pump to the water jacket on the exhaust tube.
 9. The open loop cooling water system according to claim 8, wherein the recirculation passage comprises a water jacket on a main bearing oil cooler of the marine engine.
 10. The open loop cooling water system according to claim 8, wherein the cooling water circuit upstream of the marine engine comprises a water jacket on a catalyst housing that contains a catalyst for treating exhaust gas from the marine engine, and wherein the water jacket on the exhaust tube conveys cooling water to the water jacket on the catalyst housing.
 11. The open loop cooling water system according to claim 10, wherein the cooling water circuit upstream of the marine engine comprises a water jacket on an exhaust manifold that carries exhaust gas from the marine engine to the exhaust tube, and wherein the water jacket on the catalyst housing conveys cooling water to the water jacket on the exhaust manifold.
 12. The open loop cooling water system according to claim 11, wherein the cooling water circuit downstream of the water jacket on the exhaust manifold comprises a cooling water passage through a cylinder head of the marine engine, and wherein the water jacket on the exhaust manifold conveys cooling water to the cooling water passage through the cylinder head.
 13. The open loop cooling water system according to claim 12, wherein the cooling water circuit downstream of the cooling water passage through the cylinder head comprises a cooling water passage through a cylinder block of the marine engine, and wherein the cooling water passage through the cylinder head carries cooling water through the cooling water passage of the cylinder block.
 14. The open loop cooling water system according to claim 1, wherein the recirculation pump comprises a mechanical pump that is driven by an exhaust camshaft of the marine engine.
 15. The open loop cooling water system according to claim 14, wherein the mechanical pump is mounted on the exhaust camshaft of the marine engine.
 16. The open loop cooling water system according to claim 15, wherein the mechanical pump comprises an impeller that rotates as the exhaust camshaft rotates.
 17. A method of cooling a marine engine, the method comprising pumping cooling water from upstream to downstream through a cooling water circuit that conveys cooling water from a cooling water inlet, through the marine engine, and to a cooling water outlet; pumping cooling water that is located in the cooling water circuit downstream of at least one component of the marine engine and upstream of the cooling water outlet back into the cooling water circuit upstream of the marine engine; pumping the cooling water that is located in the cooling water circuit downstream of the marine engine and upstream of the cooling water outlet to a recirculation location in the cooling water circuit that is upstream of the marine engine, wherein the recirculation location is downstream of all non-controlled exit flow paths from the cooling water circuit.
 18. (canceled)
 19. The method according to claim 17, wherein the recirculation location is located in a cooling water jacket on an exhaust tube that carries exhaust gases from the marine engine.
 20. The method according to claim 17, wherein the recirculation location is located upstream of a water jacket on a catalyst housing that contains a catalyst for treating exhaust gas from the marine engine. 